1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device, and more particularly to an inorganic dielectric film having a low dielectric constant.
2. Description of the Related Art
In order to increase a speed and to reduce power consumption in a semiconductor device, it is an important object to reduce the dielectric constant of an interlayer insulating film. The interlayer insulating film has variously been devised in order to reduce the dielectric constant. In a conventional semiconductor device, the following methods have been proposed:
(1) to add fluorine to a silica film to be an inorganic insulating film;
(2) to form an organic insulating material having a low dielectric constant as a parent material; and
(3) to intentionally form a porous film.
In the case of the method (1), however, since a heat resistance and a mechanical strength in the insulating film are deteriorated, the addition is carried out in an element ratio of several % at most. Consequently, there is a problem in that a relative dielectric constant can be reduced by only 10 to 15% of that of a conventional silica based interlayer insulating film.
In the case of the method (2), moreover, the organic material is formed. For this reason, there is a problem in that the heat resistance is considerably deteriorated as compared with a conventional silica based interlayer insulating film, resulting in a reduction in the reliability of a semiconductor element.
In the case of the method (3), furthermore, since a porous structure is random, the mechanical strength of the interlayer insulating film is remarkably reduced and the insulating film is apt to be broken in packaging, causing a reduction in the reliability of a semiconductor element.
In many cases, moreover, the porous structure is not closed. If the porous structure is not closed, the moisture resistance of the interlayer insulating film is remarkably deteriorated, causing a reduction in the reliability of the semiconductor element.
In the conventional insulating film, thus, there is a problem in that the dielectric constant cannot be reduced sufficiently, and furthermore, the mechanical strength is also insufficient.
Moreover, a line capacitance becomes a great problem in a region in which a signal line is particularly formed on the same substrate. On the other hand, in some cases, it is necessary to form a fine film having a high insulating property in a region in which a large current flows.